1. Field of the Invention
The invention relates to a method of electrode regulation of a DC arc furnace, whose arc current strength is controlled to a predeterminable set current value by means of a control signal or a rectifier correcting variable signal and whose electrode distance, i.e. the distance between at least one controllable electrode and a molten bath of the arc furnace, is controlled as a function of a difference between a predeterminable electrode regulator set value signal and an electrode regulator actual signal. The invention further relates to an electrode regulation device for a DC arc furnace for executing the method.
2. Background of the Invention
The state of the art is known from European Patent Publication EP-0 068 180 B1. There, an arc furnace with DC current supply is controlled by means of two control circuits. A current regulator assures a constant current in accordance with a preselected set current value. An electrode regulator circuit affects the position of the electrode and thus the are length. If the arc is increased, the current regulator must increase the voltage or trigger the rectifier in such a way that the current remains constant. However, this is only possible as long as there is a voltage reserve. The control of the electrode takes place by means of an adaptable DC voltage regulator. The arc voltage is used as the actual DC voltage value and is provided via a damping element to a comparator or an adder. It is necessary to calculate the set DC voltage value respectively for each working point, taking into consideration the transformer voltage step and the electrode current. It is initially limited as a function of the transformer step of the rectifier transformer, and thus the possible voltage increase of the rectifier, by means of a limiter in such a way that the rectifier is stationary operated maximally closely below the rectifier limit position. The set value is smoothed and supplied to the adder so that no overshooting of the actual value occurs with fluctuations in the voltage set value, which could cause the breaking of the arc. When the arc furnace is operated in connection with foaming slag, the efficiency of the are furnace can be reduced because of the heat radiation when the arc leaves the slag.